The invention concerns a connection system for high-pressure screwed pipe joints having a standardized retention body with a 24.degree.-connection, a likewise standardized coupling ring for producing a high-pressure connection, a pipe or a connecting member for connecting other system components and a sealing ring which is sealed by means of an elastomer high-pressure seal relative to the retention body and relative to the pipe and which has a front surface which is immediately adjacent to a front surface of the retention body.
A connection system of this kind is known in the art from DE 40 38 539 C1.
In order to manufacture appropriate high-pressure connections, in particular for fluids in high-pressure conduits, purely metallic seals of the double-edged cutting ring type are primarily used in modern day screwed pipe joints in accordance with DIN 2353 which are nearly identical from a technical point of view. The double-edged cutting ring thereby performs both a sealing as well as a holding function for the corresponding connection system. Increased demands by users have recently, however, led to an increasing desire for additional elastomer seals. Simple sealing devices for cutting rings as e. g. described in DE 41 03 266 A1 or DE 80 17 944.8 U1 as well as in DE 42 29 502 A1 have not been commercially successful up to this point in time since either the handling or the necessary pipe preparation is too difficult or expensive for the system at hand.
The most recent prior art in cutting ring systems has a connection system having two-part rings in combination with a DIN retention body with a DIN coupling ring as, e. g. described in the above cited DE 40 38 539 C1. This conventional system advantageously separates the holding function and the sealing function. As already known in the art from older publications (see e. g. DE 27 12 614 A1) and, above all, proved in practical applications, a two-part ring, due to the separated clamping and resilient functions, has substantial advantages compared to a one-part ring having a double function. In principle, the system in accordance with DE 27 12 614 A1 is distinguished from the connection system according to the above cited DE 40 38 539 C1 only in that the first system does not utilize a DIN connector and has therefore not been commercially successful.
An even older pipe coupling system is known in the art from DT 15 25 666 C3 which is particularly used for gas applications and which was not capable of achieving an improved degree of sealing using an additional elastomer seal, since the purely metallic seal described therein already guaranteed the best possible degree of sealing even in Helium leak tests of the associated coupled pipes.
The connection system in accordance with DE 40 38 539 C1 had essentially taken adopted the partial solution already known in the art from previous publications (for the sealing element e. g. DE 90 03 299.3 U1; for the cutting ring and the cutting ring sided portion of the sealing element e. g. DE 27 12 614 A1 or DT 15 25 666 C3) and transformed same into a DIN compatible form. However, the conventional system still has serious disadvantages:
All conventional block-mounted cutting rings with which a front-sided abutment surface seats in a planar, play-free manner on the front surface of the retention body, lose flexibility due to the rigid frictional connection so that premature pipe breakage on the coupling ring side and even leakage on the screw threads of the retention body can occur. The conventional system of DE 40 38 539 C1 is also block-mounted in this fashion.
During assembly, one has the general problem that although the intended end of the assembly is visible when the coupling ring is loosened, one cannot, however, observe when the cutting ring has begun to cut into the pipe and whether or not the effective cut path is sufficient for effecting the entire holding force. The conventional coupling system does not allow for the additional cutting which might be necessary, e. g. in the event that the pipe was not in complete abutment at the beginning of cutting or if the wall of the pipe is inwardly distorted.
In both cases, subsequent handling would cause a reduction in the retention force on the thread so that the coupling ring would become loosened and the elastomer seal would no longer be contained and would be pressed through the resulting gap in an outward direction. As a result of same, a subsequent tightening of the seal would no longer guarantee the sealing function. The assembler would thereby only have the option of additional tightening of the coupling ring which, however, leads, with high probability, to excessive constriction of the pipe on the 90.degree.-cone of the coupling ring so that premature pipe breakage due to shearing was nearly inevitable.
Nor would an exchange of the soft sealing element be sensible, since this would not fundamentally change the basic problem described above. Loosening of the sealing composite would again create a gap between the retention body and the sealing ring which is in any event already present at least to a certain degree from the outset due to the DIN tolerances between the sealing ring and the pipe. The single sealing element of the elastomer high pressure seal used in the conventional connecting system would then once more be drawn into the gap to no longer be able (or only partially be able) to perform its sealing function at the other side.
A completely different prior art is represented by the pipe connections having so-called tapered seal screws. For example, known from the company catalogue EMB of the company Eifeler Maschinenbau, H. Heinen GmbH & Co, D-53901 Bad Munstereifel, page VII/1, 2 (1995) is a "weld nipple screw pipe joint" with which a weld nipple having an approximately conical head is welded onto an end of a pipe intended to contain high-pressure fluid. A connector with a corresponding inner cone is then screwed against the other side of the weld nipple using a coupling ring. This type of conventional welding nipple screwed pipe joint is intended to be used, in particular, under difficult operating conditions, for example, under extreme vibration and alternating load conditions, high-pressure shocks in installations, and extreme temperature and temperature variations. In particular, this type of high-pressure screw pipe joint is utilized in installations with which down times would be associated with very high costs. A substantial disadvantage of this connecting method is, however, that the welding nipples are relatively expensive lathe components the assembly of which (welding) is also time consuming and therefore expensive and the weldment nipple leads to additional substantial inventory costs.
A substantially more economical solution is provided by a completely new type of screwed pipe joint as described in the magazine article "Competition with Old Technology" in the magazine "fluid-technik", Verlag Moderne Industrie AG, D 86895 Landsberg, page 12, 14 and 15 of July 1995. Instead of welding-on of a weld nipple, in this type of hydraulic screwed pipe joint the corresponding end of the pipe is reshaped without cutting with the assistance of an appropriate shaping machine so that, on the pipe end, a tapered seal likewise occurs as in the conventional tapered seal screw joint. This system has, however, the disadvantage that no additional soft seal is provided for. The hydraulic high-pressure sealing effect is intended to be gained solely via an area seal between the tapered outer surface of the shaped tapered seal on the pipe end and the conical inner surface in the retention body. This could hardly be tolerated in particular, in installations where down times would lead to extremely high costs. In addition, a retroactive exchange of damaged sealing elements is essentially impossible, since, when tightening the retention body against the end of the pipe using a coupling ring the tapered seal formed on the end of the pipe would most likely be deformed so that, after loosening and renewed tightening of the pipe joint, the required high-pressure sealing which might have been present following first assembly of the pipe joint would only rarely be re-established.
In contrast thereto, it is the purpose of the present invention to create a connection system having the features described above which, with as few technical changes as possible, combines the advantages of the system having a two-part ring with an improved sealing performance of less rigid systems, wherein a retroactive exchange of damaged sealing elements is facilitated and which can, in principle, be utilized not only with pipe connections having cutting rings but also with those having tapered seals.